Fw: FAT-FS HD write speed

[Thomas Doerfler]

Hello Peter,

today I have run the write data rate test. My system is a 
MC68040 with a Sandisk PCMCIA Flash Disk attached. 

For my Test I allocated a buffer of 64KByte in memory and 
write it 16 times to a file either on the flash disk or the 
root filesystem (in-memory-filesystem).

for the flash disk I got data rates of 78KByte/sec, for the 
ramdisk I reached 380KByte/sec.

So the performance of the current implementation is rather 
poor. I think about the following reasons:

- The FATs get written too often: It might be sufficent to 
update them, whenever a file is closed, I think this happens 
now whenever a new block is allocated, or so.

- The write function of our driver migt be somewhat slow. It 
has been written for "robust" functionality, not speed.

I hope this information helps you on...

wkr,
	Thomas.




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> Hi Thomas,
> 
> it would be great if you could test your write speed.
> Assuming a disk with 4000 rotations/min and further assume
> that I can write one sector per rotation it should be possible to write
> ~34kb per second.
> 
> Let's see what you can achieve.
> 
> Peter
> 
> On Fri, 10 Jan 2003 14:01:15 +0100
> "Thomas Doerfler" <Thomas.Doerfler at imd-systems.de> wrote:
> 
> > Hello,
> > 
> > sorry for not replying your first request, but 
> > christmas was near...
> > 
> > I have written a short local test to check write 
> > speed to my system, I will try it out this 
> > afternoon and given you the figures, ok? But I am 
> > working with a flash disk, so the typical problem 
> > of trying to write a sector that has just passed 
> > the write head does not occure there.
> > 
> > wkr,
> > 	Thomas.
> > 
> > 
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> > > Hello, 
> > > I sent this mail beginning of January. Because I did not get
> > > any feedback I'll try it again (now directly to you). Sorry if 
> > > you get this mail the second time.
> > > 
> > > I upload files from a PC via ftp to my embedded system
> > > (68332 at 16MHz/cs8900). A IBM 2.5" drive is used as physical storage
> > > (formatted with fat16).
> > > Download/write rates are only around 5.5kB per
> > > second. Without writing to disc (I commented out the write call in
> > > ftpd code) the download rate is about 300k/s.
> > > Next I wrote a small test app that writes 1MB dummy data directly to a
> > > file. Time required shows
> > > exacly this 5.5KB/s. So it lookes like that the filesystem code or my
> > > low level driver is the reason for the 5.5k/s. The low level driver is
> > > based on simple memory mapped data acess 
> > > following the example code from Thomas. No DMA etc.
> > > 
> > > Can you verify my figures?
> > > Any chance to make writing faster? Is there an option in the
> > > filesystem code to enable "multi sector" writes?
> > > 
> > > Thanks,
> > > Peter
> > > 
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> > --------------------------------------------
> > IMD Ingenieurbuero fuer Microcomputertechnik
> > Thomas Doerfler           Herbststrasse 8
> > D-82178 Puchheim          Germany
> > email:    Thomas.Doerfler at imd-systems.de
> > PGP public key available at: http://www.imd-
> > systems.de/pgp_key.htm
> > 
> 
> 
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--------------------------------------------
IMD Ingenieurbuero fuer Microcomputertechnik
Thomas Doerfler           Herbststrasse 8
D-82178 Puchheim          Germany
email:    Thomas.Doerfler at imd-systems.de
PGP public key available at: http://www.imd-
systems.de/pgp_key.htm